Active passive fuzing system

ABSTRACT

1. An active passive fuzing system for use in a guided missile comprising: A. MEANS FOR TRANSMITTING RADIO FREQUENCY ENERGY, B. FIRST RECEIVING CIRCUIT MEANS INCLUDING A RECEIVING ANTENNA THAT IS ORIENTED TO RECEIVE SIGNALS IN THE DIRECTION OF MISSILE FLIGHT AND SECOND RECEIVING CIRCUIT MEANS INCLUDING A RECEIVING ANTENNA ORIENTED TO RECEIVE SIGNALS IN THE DIRECTION OPPOSITE TO THE DIRECTION OF MISSILE FLIGHT FOR RECEIVING AND DETECTING SAID TRANSMITTED ENERGY REFLECTED FROM A TARGET TO BE DETECTED, C. COMPARISON CIRCUIT MEANS COUPLED TO SAID FIRST AND SECOND RECEIVING MEANS FOR COMPARING THE MAGNITUDES AND PHASE OF THE RECEIVED REFLECTED SIGNALS AND PRODUCING A DETONATING SIGNAL WHEN LIKE SIGNALS ARE RECEIVED IN EACH OF SAID FIRST AND SECOND RECEIVING MEANS, AND D. GATE CIRCUIT MEANS COUPLED TO SAID COMPARISON CIRCUIT MEANS AND BEING RESPONSIVE TO AN OUTPUT SIGNAL THEREOF TO TURN OFF SAID TRANSMITTING MEANS WHEN A COUNTERMEASURES SIGNAL OVERRIDES THE REFLECTED SIGNALS FROM THE TARGET AND TURNING SAID TRANSMITTING MEANS ON WHEN SAID COUNTERMEASURES SIGNAL CEASES.

United States Patent Holmes et al.

Oct. 21, 1975 ACTIVE PASSIVE FUZING SYSTEM Inventors: Daniel D. Holmes; Albert Weiss,

both of Riverside, Calif.

21 Appl. No.: 215,467

US. Cl 102/702 P; 343/7 PF EXEMPLARY CLAIM 1. An active passive fuzing system for use in a guided missile comprising:

a. means for transmitting radio frequency energy,

b. first receiving circuit means including a receiving antenna that is oriented to receive signals in the direction of missile flight and second receiving circuit means including a receiving antenna oriented to receive signals in the direction opposite to the direction of missile flight for receiving and detecting [52] said transmitted'energy reflected from a target to" be 51 Im. c1. F42C 13/04 detected, [58] Field of Search 102/50, 70.2; 343/5 MD, 0. comparison circuit means coupled to said first and 343/7 second receiving means for comparing the magnitudes and phase of the received reflected signals and [56] References Cited producing a detonating signal when like signals are UNITED STATES PATENTS received in each of said first and second receiving 2,845,619 7/1958 Rawlins 343/7 means and 2,931,300 4/1960 Lord et al. d. gate circuit means coupled to said comparison 3,068,468 12/1962 Bretscher et al. 343/5 MD circuit means and being responsive to an output signal Primary Examiner-Harvey E. Behrend Assistant ExaminerC. T. Jordan Attorney, Agent, 0r FirmRichard S. Sciascia; Joseph M. St. Amand; T. M. Phillips TARGET thereof to turn off said transmitting means when a countermeasures signal overrides the reflected signals from the target and turning said transmitting means on when said countermeasures signal ceases.

4 Claims, 1 Drawing Figure '0 I4 MISSILE FLIGHT DIRECTION 0B l r 26 l 20 CIRCU US Patent Oct. 21, 1975 3,913,485

TARGET I6 l4 MISSILE FLIGHT Y DIRECTION CHANNEL cHANNEL ONE TRANSMITTER TWO ogc ATE CIRCUIT G F 7 2 f 4 I I DIFFERENTIAL I i I AMPLIFIER 27 I I PHASE I I SENSITIVE I I DETECTOR I I L 91 1"3 1 ':3E I

[3O DANIEL D. HOLMES ALBERT WEISS DETONATION INVENTORS CIRCUIT BY JQWZ W ATTORNEYS 1 ACTIVE PASSIVE FUZING SYSTEM The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to an active passive fuzing system and more particularly to an active passive fuzing system which minimizes the probability of premature fuze detonation or deactivation (dudding) due to undesired signals such as enemy countermeasures or other external interfering signals.

The present invention provides a simple effective system which utilizes a single transmitting antenna and two receiving antennas oriented at angles a and B respectively, as referred to the transmitting antenna. Angles a and B are chosen so as to provide a coincidental coverage of the smallest target at a distance not exceeding the lethal effectiveness of the missile warhead.

Accordingly, an object of the present invention is to provide a fuzing system which is simple to construct but effective in the environment of undesired signals such as enemy countermeasures or other external interfering signals.

Other objects and many of the attendant advantages of this invention will become readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein there is shown in a single FIGURE a preferred embodiment of the invention.

Referring now to the drawing there is shown a radio frequency energy transmitting antenna and two receiving antennas l2 and 14 for transmitting energy in the direction of target 16 and for receiving reflected energy therefrom. Antenna 12 is positioned to look ahead at an angle a in the direction of flight and sees target 16 first and antenna 14 is positioned to look in the opposite direction at an angle B, as referred to antenna 10. There is a receiving channel associated with each of the receiving antennas; antenna 12 is coupled to channel one, designated by numeral 18, and antenna 14 is coupled to channel two, designated by the numeral 20. The output from channel one, 18, feeds an automatic gain control circuit, 22, and a comparision circuit, 24. Channel two, 20, also feeds into comparison circuit, 24. The output of automatic gain control circuit 22 is connected to channels 18 and 20 to control their gain. Transmitting antenna 10 is coupled to a transmitter 26 which is controlled by gating circuit 28. Channels 18 and 20 may be of any of the well known receiving and detecting channels of radar system restricted to the frequency of transmitter 26. Transmitter 26 may be of any of the standard radar transmitters available on the market. Comparison circuit 24 comprises a differential amplifier 25 which compares the negative amplitudes of the signals from channels one and two.

The output of the amplifier is a function of the disimilarity of the signals in channels one and two. Regardless of amplitude, signals which are similar in amplitude and phase give essentially no output. In the event of a countermeasure signal being received by either channel, the output is essentially proportional to the received signal. At a predetermined level the output from the differential amplifier 25 will activate the gate 28 turning off the transmitter. This places the system in the passive state. The differential amplifier is standard circuitry of the type described on page 10 and FIG. 10 of the text Functional Circuits and Oscillators" by Herbert J. Reich. The gate 28 is standard circuitry as described in pages 47 to 58 of the same text.

The output of the phase sensitive detector 27 is a function of the relative amplitude and phase of the signals in channels one and two. When the signal in channel one reaches a predetermined level and its phase is consistent with the signal in channel two, the detector 27 will produce an output proportional to the signal in channel two. When the amplitudes rise to the predetermined level and the phase approaches identity, the output rises and actuates the detonation circuit 30. The phase sensitive detector 27 is standard circuitry as described on page 141, FIGS. 8-18 of the text Principles of Electronic Instruments by Gordon R. Partridge. There would be a d.c. bias on the diodes to set the predetermined signal level for triggering the detonation circuit 30. The detonation circuit 30 can be any desired circuit as is used in current fuze design.

In operation, a radio wave is transmitted via antenna 10 by transmitter 26. As the missile (not shown) on which the fuzing system is mounted intercepts target 16, the transmitted energy is reflected into the receiving antennas 12 and 14. The relative magnitudes and phase are functions of the angles a and B and the position of target 16 with respect to antennas l0, l2 and 14. The absolute magnitude is dependent upon missiletargetdistance, target size, target structure, etc.. The phase is a function of the respective path lengths from antenna 10 to target 16 and back to antennas 12 and 14. The reflected radiation as received by antennas l2 and 14 is detected and amplified by channels 18 and 20 respectively. The output of channel 18 feeds automatic gain control circuit 22 and comparison circuit 24. The output of control circuit 22 controls the amplification of channels 18 and 20, by negative feedback which is a function of the signal level in antenna 12. The operation of control circuit 18 is such that it operates to reduce the gain of both channels proportionately to an increase in the signal level at antenna 10 above the normal target signal, should there be a lack of corresponding signal at antenna 12 to indicate the proximity of an actual target. The presence of an actual target will cause the outputs of channels 18 and 20 to reach a predetermined similarity in amplitudes and/or similarity or dissimilarity in phase. Comparison circuit 24 will produce an output signal to actuate detonation circuit 30 at the optimum point for the missile warhead.

In the event of countermeasures action from target 16 originating at a point in space other than the optimum detonation point, the outputs of channels 18 and 20 would produce greatly dissimilar amplitudes at comparison circuit 24. The duration of this dissimilarity at amplitudes above the detectability threshold will be long compared to the normal fuzing signal because of transmitter 26 power and the orientation and characteristics of antennas 10, 12 and 14, i.e., if the countermeasures signal originates from a point in space external to the coincidental coverage of antennas 12 and 14. When the amplitude of the countermeasures signal reaches a predetermined value in channel 18, gate 28 is actuated, turning off transmitter 26. As the system approaches the transmitted countermeasures signal, the signals received by antennas 12 and 14 are compared by comparison circuit 24. When the signals are similar in amplitude and reach the required similarity and/or dissimilarity in phase, circuit 24 produces an output signal to initiate detonation circuit 30 in the same manner as described above. Automatic gain control circuit 22 also serves to prevent saturation of either channel, with a resulting premature firing of the system. Should the countermeasures signal be turned off before target intercept, gate 28 will turn transmitter 26 on and the system reverts to active operation as described above. In either active or passive operation, the system functions to initiate detonation circuit 30 only when the radiation received by antennas l2 and 14 are similar in amplitude and/or phase. This similarity occurs only in a narrow region between the antennas. Thus, the burst position of the system is defined and can be controlled by the beam width of the antennas and the angular displacement of the antennas. In the event countermeasures signals are present, the system becomes passive and functions at the normal burst position, on the radiation from the countermeasures source.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. An active passive fuzing system for use in a guided missile comprising:

a. means for transmitting radio frequency energy,

b. first receiving circuit means including a receiving antenna that is oriented to receive signals in the direction of missile flight and second receiving circuit means including a receiving antenna oriented to receive signals in the direction opposite to the direction of missile flight for receiving and detecting said transmitted energy reflected from a target to be detected,

0. comparison circuit means coupled to said first and second receiving means for comparing the magnitudes and phase of the received reflected signals and producing a detonating signal when like signals are received in each of said first and second receiving means, and

d. gate circuit means coupled to said comparison circuit means and being responsive to an output signal thereof to turn off said transmitting means when a countermeasures signal overrides the reflected signals from the target and turning said transmitting means on when said countermeasures signal ceases.

2. An active passive fuzing system for use in a guided missile comprising:

a. means for transmitting radio frequency energy,

b. first receiving circuit means including a receiving antenna that is oriented to receive signals in the direction of missile flight and second receiving circuit means including a receiving antenna oriented to receive signals in the direction opposite to the direction of missile flight for receiving and detecting said transmitted energy reflected from a target to be detected,

0. comparison circuit means coupled to said first and second receiving means for comparing the magnitudes and phase of the received signals and producing a detonating signal when like signals are received in each of said first and second receiving means,

d. automatic gain control circuit means having an input coupled to the output of the first receiving circuit means and having a first output coupled as an input to said first receiving circuit means and a second output coupled as an input to the second receiving circuit means for reducing the gains of both receiving circuits proportionately to an increase in the level of the received signals, and

e. gate circuit means coupled to said comparison circuit means and being responsive to an output signal thereof to turn off said transmitting means when a countermeasure signal overrides the reflected signal from the target and for turning said transmitting on when said countermeasures signal ceases.

3. An active passive fuzing system for use in a guided missile comprising:

a. means for transmitting radio frequency energy,

b. first receiving circuit means including a receiving antenna that is oriented to receive signals in the direction of missile flight and second receiving circuit means including a receiving antenna oriented to receive signals in the direction opposite to the direction of missile flight for receiving and detecting said transmitted energy reflected from a target to be detected,

0. comparison circuit means coupled to said first and second receiving means for comparing the magnitude and phase of the received reflected signals and producing a detonating signal when like signals are received in each of said first and second receiving means, and

d. means coupled to said comparison circuit means and to said transmitting means for turning off said transmitting means when signals of dissimilar predetermined amplitudes persist for a predetermined time.

4. An active passive fuzing system for use in a guided missile comprising:

a. means for transmitting radio frequency energy,

b. first receiving circuit means including a receiving antenna that is oriented to receive signals in the direction of missile flight and second receiving circuit means including a receiving antenna oriented to receive signals in the direction opposite to the direction of missile flight for receiving and detecting said transmitted energy reflected from a target to be detected,

c. comparison circuit means coupled to said first and second receiving means for comparing the magnitude and phase of the received reflected signals and producing a detonating signal when like signals are received in each of said first and second receiving means, and

d. means coupled to said comparison circuit means and to said transmitting means for turning off said transmitting means in the presence of countermeasures signals. 

1. An active passive fuzing system for use in a guided missile comprising: a. means for transmitting radio frequency energy, b. first receiving circuit means including a receiving antenna that is oriented to receive signals in the direction of missile flight and second receiving circuit means including a receiving antenna oriented to receive signals in the direction opposite to the direction of missile flight for receiving and detecting said transmitted energy reflected from a target to be detected, c. comparison circuit means coupled to said first and second receiving means for comparing the magnitudes and phase of the received reflected signals and producing a detonating signal when like signals are received in each of said first and second receiving means, and d. gate circuit means coupled to said comparison circuit means and being responsive to an output signal thereof to turn off said transmitting means when a countermeasures signal overrides the reflected signals from the target and turning said transmitting means on when said countermeasures signal ceases.
 2. An active passive fuzing system for use in a guided missile comprising: a. means for transmitting radio frequency energy, b. first receiving circuit means including a receiving antenna that is oriented to receive signals in the direction of missile flight and second receiving circuit means including a receiving antenna oriented to receive signals in the direction opposite to the direction of missile flight for receiving and detecting said transmitted energy reflected from a target to be detected, c. comparison circuit means coupled to said first and second receiving means for comparing the magnitudes and phase of the received signals and producing a detonatiNg signal when like signals are received in each of said first and second receiving means, d. automatic gain control circuit means having an input coupled to the output of the first receiving circuit means and having a first output coupled as an input to said first receiving circuit means and a second output coupled as an input to the second receiving circuit means for reducing the gains of both receiving circuits proportionately to an increase in the level of the received signals, and e. gate circuit means coupled to said comparison circuit means and being responsive to an output signal thereof to turn off said transmitting means when a countermeasure signal overrides the reflected signal from the target and for turning said transmitting on when said countermeasures signal ceases.
 3. An active passive fuzing system for use in a guided missile comprising: a. means for transmitting radio frequency energy, b. first receiving circuit means including a receiving antenna that is oriented to receive signals in the direction of missile flight and second receiving circuit means including a receiving antenna oriented to receive signals in the direction opposite to the direction of missile flight for receiving and detecting said transmitted energy reflected from a target to be detected, c. comparison circuit means coupled to said first and second receiving means for comparing the magnitude and phase of the received reflected signals and producing a detonating signal when like signals are received in each of said first and second receiving means, and d. means coupled to said comparison circuit means and to said transmitting means for turning off said transmitting means when signals of dissimilar predetermined amplitudes persist for a predetermined time.
 4. An active passive fuzing system for use in a guided missile comprising: a. means for transmitting radio frequency energy, b. first receiving circuit means including a receiving antenna that is oriented to receive signals in the direction of missile flight and second receiving circuit means including a receiving antenna oriented to receive signals in the direction opposite to the direction of missile flight for receiving and detecting said transmitted energy reflected from a target to be detected, c. comparison circuit means coupled to said first and second receiving means for comparing the magnitude and phase of the received reflected signals and producing a detonating signal when like signals are received in each of said first and second receiving means, and d. means coupled to said comparison circuit means and to said transmitting means for turning off said transmitting means in the presence of countermeasures signals. 